1. Technical Field of the Invention
The present invention relates to the screening of packet traffic at multiple levels and, in particular, to a hierarchical screening technique where the filter screen criteria at each level may be dynamically selected based on, for example, processing capabilities at each level and/or variations in packet traffic mix.
2. Description of Related Art
The need to screen packet traffic arises in a number of recognized scenarios. One such scenario is in the context of a network intrusion detection system (IDS) application where passing packet traffic is examined for threatening or dangerous content. When such a threat is detected, the suspect packet traffic is identified and captured or dropped (perhaps using a firewall) before it has a chance to enter a protected network.
It is known that the screening operation performed to examine the packet traffic takes time and thus can delay packet traffic transport throughput. This delay concern is magnified as the volume of traffic to be examined increases and the intrusion detection system presents a potential bottleneck to packet traffic passage. Further delays in throughput time result from the use of more comprehensive (and time consuming) screening operations.
A need accordingly exists for a more efficient approach to packet screening.